No heat , gurgling sound coming from glove box area

SOURCE: 1998 ford f150- heat issue

There is no heater valve on a 1998 ford F-150. The hoses for the heater lead directly from the engine and go to the heater case. PS The heater doors are all vacuum controlled so you might wanna look under the dash for any lines that might be disconnected

SOURCE: heater doesn't work. A/C works and air blows, but

There are 3 possible cases: 1- The Flap Divert air direction valve for air flowing through the heater core is not doing its job. 2- The heater core gets clogged up. 3- The valve to control amount of hot coolant flow to heater core gets stuck. Let's check if the water can flow to the heater core first, by disconnect the output hose from heater core while running the engine with heater set up at maximum level to see if coolant flowing out. Catch this coolant with a container to refill it back. This way you can eliminate # 2 and # 3. Good luck.

SOURCE: 1999 ford taurus no heat

Is the blower motor working? If not that is what it is. If it is working then check heater coil out, Could be bad heater coil.

SOURCE: 1999 Ford Taurus, no heat.

Try checking the two pipes that go into and come out of the heater matrix, is one of them hot? if it is there is an air lock within the matrix, Also is the thermostat opening fully? Sorry i know you said you have changed it twice already but take it out check settings when it should open and close, then boil some water and test the thermostat

SOURCE: Have no heat. Have replaced heater core,

I don't know your vehicle, but does it have a blower door tucked in where the heater core is? If it DOES and that's broken then it could be the whole problem. It would mean it isn't switching from the A/C side of things to the heat side of them. Hope this helps, good luck! Also, just looked up the proper name for what I'm talking about, it's called a "blend door" and I think your car has one. It's what I would check, again, good luck!